1. Technical Field
The present disclosure is directed to electrosurgery and, in particular, to an electrosurgical electrode having a non-conductive porous ceramic coating for controlling the amount of current per arc.
2. Description of the Related Art
Tissue heating is proportional to the square of the amount of current being generated through the tissue and tissue vaporization is, in turn, generally proportional to current. Vaporization of tissue is proportional to the amount of energy in the arc. This energy, in combination with the Cathode Fall Voltage, derives the power for vaporization. Thermal spread is dependent on the amount of heat generated within the tissue and is dependent on tissue resistivity and the arc energy squared. As can be appreciated, by not controlling the thermal spread the depth of ablation is difficult to predict and control.
Therefore, during electrosurgery, an increase or decrease in the amount of current provides a different tissue effect. This phenomenon is due to a variable referred to as the crest factor (CF). The crest factor can be calculated using the formula: CF=VPEAK/VRMS, where VPEAK is the positive peak of the waveform and VRMS is the RMS value of the waveform. The crest factor can also be calculated using the formula: CF=[(1-D)/D]1/2, where D is the duty cycle of the waveform and is defined as D=T1/(T1+T2).
Based on the above formulas, it is evident that when operating an electrosurgical generator system in either the “cut”, “blend” or “coagulate” mode, the range of the crest factor varies from one mode to another. For example, the “cutting” mode typically entails generating an uninterrupted sinusoidal waveform in the frequency range of 100 kHz to 4 MHz with a crest factor in the range of 1.4 to 2.0. The “blend” mode typically entails generating an uninterrupted cut waveform with a duty cycle in the range of 25% to 75% and a crest factor in the range of 2.0 to 5.0. The “coagulate” mode typically entails generating an uninterrupted waveform with a duty cycle of approximately 10% or less and a crest factor in the range of 5.0 to 12.0. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass with significantly-reduced demarcation between the opposing tissue structures (opposing walls of the lumen). Coagulation of small vessels is usually sufficient to permanently close them. Larger vessels need to be sealed to assure permanent closure.
An increase in the crest factor results in more current per arc at a given power setting. Further, since tissue heating is proportional to the amount of current through the tissue squared and tissue vaporization is proportional to the amount of current being generated through the tissue, a doubling of current per arc results in four times as much tissue heating and twice the amount of tissue vaporization when an electrode connected to the electrosurgical generator system contacts the tissue. Known electrodes cannot control or limit the current per arc to achieve a particular surgical effect, e.g., a fine cut. Accordingly, such electrodes do not have the ability to manipulate or control the proportion of tissue vaporization to tissue heating, in order to achieve more controllable and desirable surgical effects.
Therefore, it is an aspect of the present disclosure to provide an electrosurgical electrode capable of controlling or limiting the current per arc for controlling the both tissue heating and tissue vaporization.